Jump-ratio map

Two techniques are commonly used in EFTEM to map elemental distribution: 2-window ratio mapping and 3-window elemental mapping. The jump-ratio approach requires two energy-filtered images, one you position just before the ionization edge (pre-edge) and one you position just after the edge (post-edge). In the jump-ratio approach the post-edge image is divided by the corresponding pre-edge image to produce a map that is indicative of the distribution of the element you select.

To acquire a jump-ratio map, specify

Element of interest

Camera parameters

Slit width and filter energies to be used for the pre- and post-edge acquisitions

Access the Configure Jump Ratio dialog will vary based on the mode you choose

SingleMap mode – Press the Select Jump-Ratio Map button

MultiMap mode – Specify via the MultiMap Configuration dialog

Indicate parameters within the Configure Jump Ratio dialog

Window settings (eV)

Setup – Allows you to recall pre-saved or default settings for a particular element

Slit width – Specify the energy-selecting slit width you want to use for both the pre- and post-edge acquisitions

Post-edge – Designate the energy loss setting that the filter will use to acquire the post-edge image

Pre-edge – Indicate the energy loss setting that the filter will use to acquire the pre-edge image

Edge – Specify the edge you want to use for ratio mapping

Detector – Specify the detector settings you want to use

Spectrum display – Generates and displays a simulated spectrum at the top of the dialog to give you visual feedback regarding the feature shape and the selected acquisition window positions

Click Capture

The routine will

Acquire the post-edge image followed by the post-edge image

Correct for any spatial drift between the images

Compute and display the ratio map

When you create a jump-ratio map, first insert the slit and focus the image at an energy loss (typically 400 eV and 50 eV slit) before acquiring a pre-edge image. Acquire the pre-edge image, and then shift the energy to after the edge to acquire the post-edge image. To calculate the ratio, divide the post- by the pre-edge image value.